I got so many .blend files in my C:/tmp folder....is it safe to delete some of them?
Most files in temp folder are either autosaves, temporary backups, clipboard items (when using copy-paste through Ctrl + C > Ctrl + V) or expendable cache files.

Unless you recently lost any work and some file needs recovery, you worked on some unsaved projects, or Blender crashed or unexpectedly closed and you didn't save your work before, non of those files should be important, and can be safely removed without issues.

Blender doesn't normally store important files in unsafe locations, so unless you specifically told it to (either explicitly or by omission) files in temp locations should be unimportant and discardable.

Be sure that all your files are correctly saved in some "projects" folder in a safe spot in your hard drive. If in doubt use your system's safe deletion system (Recycle Bin for Windows) when deleting so that if something goes wrong you can restore it.